A touch-sensitive screen, or “touch screen”, is an electronic visual display that can detect the presence and location of a touch within the display area. The term generally refers to touching the display of the device with a finger, a hand or another passive object, such as a stylus. The touch screen enables a user to interact directly with what is displayed, rather than indirectly with a cursor controlled by a mouse or touchpad.
There are a variety of touch screen technologies. The two most popular technologies are resistive and capacitive touch screens. A resistive touch screen panel is composed of several layers of which two are thin, metallic, electrically conductive layers which are separated by a narrow gap. When an object, such as a finger, presses down on a point on the panel's outer surface the two metallic layers become connected at that point: the panel then behaves as a pair of voltage dividers with connected outputs. This causes a change in the electrical current, which is registered as a touch event and sent to a controller for processing.
A capacitive touch screen panel consists of an insulator such as glass, coated with a transparent conductor such as indium tin oxide. As the human body is also a conductor, touching the surface of the screen with a finger for example results in a distortion of the screen's electrostatic field, measurable as a change in capacitance. Different technologies may be used to determine the location of the touch. The location is then sent to a controller for processing.
There are typically four layers in a resistive or capacitive touch screen; a top polyester layer coated with a transparent metallic conductive coating on the bottom, an adhesive spacer, a glass layer coated with a transparent metallic conductive coating on the top and an adhesive layer on the backside of the glass for mounting. The touch screen is normally illuminated using a backlight.